Increasing Acidity

Long-simmered brown sauces, even when carefully prepared with the best ingredients, often taste flat, usually because during the long reduction, the volatile flavor components in the meats, herbs, and vegetables have been cooked off. A small amount of good-quality wine vinegar (anywhere from a few drops to a few teaspoons per cup/250 milliliters sauce) added to the sauce near the end will awaken the flavor.